MESOSCALE PRECIPITATION DISCUSSION 0607
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
451 AM EDT SAT OCT 24 2015
AREAS AFFECTED...TEXAS
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY
VALID 240850Z - 241450Z
SUMMARY...INCREASING COVERAGE OF INCREASINGLY EFFICIENT HEAVY
RAINFALL PRODUCING CONVECTION AHEAD OF REMNANTS OF PATRICIA AND
STRENGTHENING SURFACE BOUNDARY.
DISCUSSION...MID-LEVEL CIRCULATION OF PATRICIA ALREADY THROUGH
CENTRAL PLATEAU OF MEXICO STARTING TO BRING BROAD SCALE ASCENT
WITH VAST AREA OF DPVA. ADDITIONAL BAROCLINIC SUPPORT FROM BROAD
ENTRANCE REGION DYNAMICS OF 140KT JET (PER SATELLITE DERIVED WINDS
IN NE OK) AS WELL AS CONVERGING FRONTAL ZONES SUPPORT THIS LARGE
SCALE UVV ZONE ACROSS MUCH OF CENTRAL AND SOUTHERN TEXAS. SOUTH
OF THE FRONTS...SATURATED PROFILES TO NEARLY 400 MB WITH AMPLE
TPWS EXCEEDING 2 TO 2.5" WILL BE ADVECTED WITH LIMITED BUT
SUFFICIENT INSTABILITY ALONG WIDE 20-30 KT 20-30KT 85H TO 7H
UNIDIRECTIONAL SOUTHERLY FLOW WHICH WILL CONTINUE TO BE NEARLY
PERPENDICULAR TO THE FRONTAL ZONE FOR STRONG ISENTROPIC LIFT TO
SUPPORT CONVECTIVE GROWTH AND EFFICIENT RAINFALL PRODUCTION.
RATES IN EXCESS OF 2.0"/HR ARE LIKELY WITH VERY SLOW SOUTHWARD
PROGRESSION OF THE FRONT WITH TIME TO ALLOW FOR A BROAD ZONE OF
2-4" FROM THE BIG BEND/DRT EASTWARD TOWARD A WEAK SURFACE
INFLECTION NEAR BMQ...CURRENTLY.
AT THIS SURFACE LOW...A N-S BOUNDARY PARALLEL TO THE WEST GULF
COAST DROPS SOUTH TO BRO. THIS BOUNDARY IS ACTING AS AN
ADDITIONAL MID-LEVEL CONVERGENCE BOUNDARY FOR CONVECTION TO
DEVELOP/ENHANCE FROM SWLY FLOW FROM PATRICIA. WITH THE BULK OF
THE CLOUD BARING LAYER GENERALLY UNIDIRECTIONAL...THIS CONVECTION
WITH ITS 2-2.5"/HR RATES WILL TRAIN OVER THE SAME SMALL CORRIDOR
FROM BRO TO ALI TO SAT WITH TOTALS OF 2-4" EXPECTED IN THE NEXT
6HRS OR SO. ONCE THIS CHANNEL OF ENHANCED CONVECTION INSECTS THE
STATIONARY FRONT...INCREASED MERGERS AND RAINFALL EFFICIENCY IS
EXPECTED WITH RATES OF 3"/HR POSSIBLE AND A ZONE OF EXTREME
RAINFALL TOTALS NEAR 6" WITH LIKELY LOCALIZE HIGHER AMOUNTS FOR
THE POTENTIAL FOR EXCESSIVE FLASH FLOODING CONDITIONS. THIS IS
SUGGESTED BY RECENT RUNS OF THE HRRR...CANADIAN GEM REGIONAL.
WITH ENHANCED OUTFLOW CHANNEL TO THE NORTHEAST...MODERATE TO HEAVY
STRATIFORM RAINFALL WILL COMPOUND ALREADY SATURATED AREAS
NEAR/SOUTH OF THE DFW METRO...MAINTAINING FLASH FLOOD/PROLONGED
FLOODING CONDITIONS THERE AS WELL.
GALLINA
ATTN...WFO...BRO...CRP...EWX...FWD...HGX...SHV...SJT...